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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.util.concurrent;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkArgument;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.20"></a>
<span class="sourceLineNo">021</span><a name="line.21"></a>
<span class="sourceLineNo">022</span>import com.google.common.annotations.Beta;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import com.google.common.annotations.VisibleForTesting;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.base.Throwables;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import com.google.common.collect.Lists;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import com.google.common.collect.Queues;<a name="line.26"></a>
<span class="sourceLineNo">027</span><a name="line.27"></a>
<span class="sourceLineNo">028</span>import java.lang.reflect.InvocationTargetException;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import java.util.Collection;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import java.util.Collections;<a name="line.30"></a>
<span class="sourceLineNo">031</span>import java.util.Iterator;<a name="line.31"></a>
<span class="sourceLineNo">032</span>import java.util.List;<a name="line.32"></a>
<span class="sourceLineNo">033</span>import java.util.concurrent.BlockingQueue;<a name="line.33"></a>
<span class="sourceLineNo">034</span>import java.util.concurrent.Callable;<a name="line.34"></a>
<span class="sourceLineNo">035</span>import java.util.concurrent.ExecutionException;<a name="line.35"></a>
<span class="sourceLineNo">036</span>import java.util.concurrent.ExecutorService;<a name="line.36"></a>
<span class="sourceLineNo">037</span>import java.util.concurrent.Executors;<a name="line.37"></a>
<span class="sourceLineNo">038</span>import java.util.concurrent.Future;<a name="line.38"></a>
<span class="sourceLineNo">039</span>import java.util.concurrent.RejectedExecutionException;<a name="line.39"></a>
<span class="sourceLineNo">040</span>import java.util.concurrent.ScheduledExecutorService;<a name="line.40"></a>
<span class="sourceLineNo">041</span>import java.util.concurrent.ScheduledFuture;<a name="line.41"></a>
<span class="sourceLineNo">042</span>import java.util.concurrent.ScheduledThreadPoolExecutor;<a name="line.42"></a>
<span class="sourceLineNo">043</span>import java.util.concurrent.ThreadFactory;<a name="line.43"></a>
<span class="sourceLineNo">044</span>import java.util.concurrent.ThreadPoolExecutor;<a name="line.44"></a>
<span class="sourceLineNo">045</span>import java.util.concurrent.ThreadPoolExecutor.CallerRunsPolicy;<a name="line.45"></a>
<span class="sourceLineNo">046</span>import java.util.concurrent.TimeUnit;<a name="line.46"></a>
<span class="sourceLineNo">047</span>import java.util.concurrent.TimeoutException;<a name="line.47"></a>
<span class="sourceLineNo">048</span>import java.util.concurrent.locks.Condition;<a name="line.48"></a>
<span class="sourceLineNo">049</span>import java.util.concurrent.locks.Lock;<a name="line.49"></a>
<span class="sourceLineNo">050</span>import java.util.concurrent.locks.ReentrantLock;<a name="line.50"></a>
<span class="sourceLineNo">051</span><a name="line.51"></a>
<span class="sourceLineNo">052</span>/**<a name="line.52"></a>
<span class="sourceLineNo">053</span> * Factory and utility methods for {@link java.util.concurrent.Executor}, {@link<a name="line.53"></a>
<span class="sourceLineNo">054</span> * ExecutorService}, and {@link ThreadFactory}.<a name="line.54"></a>
<span class="sourceLineNo">055</span> *<a name="line.55"></a>
<span class="sourceLineNo">056</span> * @author Eric Fellheimer<a name="line.56"></a>
<span class="sourceLineNo">057</span> * @author Kyle Littlefield<a name="line.57"></a>
<span class="sourceLineNo">058</span> * @author Justin Mahoney<a name="line.58"></a>
<span class="sourceLineNo">059</span> * @since 3.0<a name="line.59"></a>
<span class="sourceLineNo">060</span> */<a name="line.60"></a>
<span class="sourceLineNo">061</span>public final class MoreExecutors {<a name="line.61"></a>
<span class="sourceLineNo">062</span>  private MoreExecutors() {}<a name="line.62"></a>
<span class="sourceLineNo">063</span><a name="line.63"></a>
<span class="sourceLineNo">064</span>  /**<a name="line.64"></a>
<span class="sourceLineNo">065</span>   * Converts the given ThreadPoolExecutor into an ExecutorService that exits<a name="line.65"></a>
<span class="sourceLineNo">066</span>   * when the application is complete.  It does so by using daemon threads and<a name="line.66"></a>
<span class="sourceLineNo">067</span>   * adding a shutdown hook to wait for their completion.<a name="line.67"></a>
<span class="sourceLineNo">068</span>   *<a name="line.68"></a>
<span class="sourceLineNo">069</span>   * &lt;p&gt;This is mainly for fixed thread pools.<a name="line.69"></a>
<span class="sourceLineNo">070</span>   * See {@link Executors#newFixedThreadPool(int)}.<a name="line.70"></a>
<span class="sourceLineNo">071</span>   *<a name="line.71"></a>
<span class="sourceLineNo">072</span>   * @param executor the executor to modify to make sure it exits when the<a name="line.72"></a>
<span class="sourceLineNo">073</span>   *        application is finished<a name="line.73"></a>
<span class="sourceLineNo">074</span>   * @param terminationTimeout how long to wait for the executor to<a name="line.74"></a>
<span class="sourceLineNo">075</span>   *        finish before terminating the JVM<a name="line.75"></a>
<span class="sourceLineNo">076</span>   * @param timeUnit unit of time for the time parameter<a name="line.76"></a>
<span class="sourceLineNo">077</span>   * @return an unmodifiable version of the input which will not hang the JVM<a name="line.77"></a>
<span class="sourceLineNo">078</span>   */<a name="line.78"></a>
<span class="sourceLineNo">079</span>  @Beta<a name="line.79"></a>
<span class="sourceLineNo">080</span>  public static ExecutorService getExitingExecutorService(<a name="line.80"></a>
<span class="sourceLineNo">081</span>      ThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {<a name="line.81"></a>
<span class="sourceLineNo">082</span>    return new Application()<a name="line.82"></a>
<span class="sourceLineNo">083</span>        .getExitingExecutorService(executor, terminationTimeout, timeUnit);<a name="line.83"></a>
<span class="sourceLineNo">084</span>  }<a name="line.84"></a>
<span class="sourceLineNo">085</span><a name="line.85"></a>
<span class="sourceLineNo">086</span>  /**<a name="line.86"></a>
<span class="sourceLineNo">087</span>   * Converts the given ScheduledThreadPoolExecutor into a<a name="line.87"></a>
<span class="sourceLineNo">088</span>   * ScheduledExecutorService that exits when the application is complete.  It<a name="line.88"></a>
<span class="sourceLineNo">089</span>   * does so by using daemon threads and adding a shutdown hook to wait for<a name="line.89"></a>
<span class="sourceLineNo">090</span>   * their completion.<a name="line.90"></a>
<span class="sourceLineNo">091</span>   *<a name="line.91"></a>
<span class="sourceLineNo">092</span>   * &lt;p&gt;This is mainly for fixed thread pools.<a name="line.92"></a>
<span class="sourceLineNo">093</span>   * See {@link Executors#newScheduledThreadPool(int)}.<a name="line.93"></a>
<span class="sourceLineNo">094</span>   *<a name="line.94"></a>
<span class="sourceLineNo">095</span>   * @param executor the executor to modify to make sure it exits when the<a name="line.95"></a>
<span class="sourceLineNo">096</span>   *        application is finished<a name="line.96"></a>
<span class="sourceLineNo">097</span>   * @param terminationTimeout how long to wait for the executor to<a name="line.97"></a>
<span class="sourceLineNo">098</span>   *        finish before terminating the JVM<a name="line.98"></a>
<span class="sourceLineNo">099</span>   * @param timeUnit unit of time for the time parameter<a name="line.99"></a>
<span class="sourceLineNo">100</span>   * @return an unmodifiable version of the input which will not hang the JVM<a name="line.100"></a>
<span class="sourceLineNo">101</span>   */<a name="line.101"></a>
<span class="sourceLineNo">102</span>  @Beta<a name="line.102"></a>
<span class="sourceLineNo">103</span>  public static ScheduledExecutorService getExitingScheduledExecutorService(<a name="line.103"></a>
<span class="sourceLineNo">104</span>      ScheduledThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {<a name="line.104"></a>
<span class="sourceLineNo">105</span>    return new Application()<a name="line.105"></a>
<span class="sourceLineNo">106</span>        .getExitingScheduledExecutorService(executor, terminationTimeout, timeUnit);<a name="line.106"></a>
<span class="sourceLineNo">107</span>  }<a name="line.107"></a>
<span class="sourceLineNo">108</span><a name="line.108"></a>
<span class="sourceLineNo">109</span>  /**<a name="line.109"></a>
<span class="sourceLineNo">110</span>   * Add a shutdown hook to wait for thread completion in the given<a name="line.110"></a>
<span class="sourceLineNo">111</span>   * {@link ExecutorService service}.  This is useful if the given service uses<a name="line.111"></a>
<span class="sourceLineNo">112</span>   * daemon threads, and we want to keep the JVM from exiting immediately on<a name="line.112"></a>
<span class="sourceLineNo">113</span>   * shutdown, instead giving these daemon threads a chance to terminate<a name="line.113"></a>
<span class="sourceLineNo">114</span>   * normally.<a name="line.114"></a>
<span class="sourceLineNo">115</span>   * @param service ExecutorService which uses daemon threads<a name="line.115"></a>
<span class="sourceLineNo">116</span>   * @param terminationTimeout how long to wait for the executor to finish<a name="line.116"></a>
<span class="sourceLineNo">117</span>   *        before terminating the JVM<a name="line.117"></a>
<span class="sourceLineNo">118</span>   * @param timeUnit unit of time for the time parameter<a name="line.118"></a>
<span class="sourceLineNo">119</span>   */<a name="line.119"></a>
<span class="sourceLineNo">120</span>  @Beta<a name="line.120"></a>
<span class="sourceLineNo">121</span>  public static void addDelayedShutdownHook(<a name="line.121"></a>
<span class="sourceLineNo">122</span>      ExecutorService service, long terminationTimeout, TimeUnit timeUnit) {<a name="line.122"></a>
<span class="sourceLineNo">123</span>    new Application()<a name="line.123"></a>
<span class="sourceLineNo">124</span>        .addDelayedShutdownHook(service, terminationTimeout, timeUnit);<a name="line.124"></a>
<span class="sourceLineNo">125</span>  }<a name="line.125"></a>
<span class="sourceLineNo">126</span><a name="line.126"></a>
<span class="sourceLineNo">127</span>  /**<a name="line.127"></a>
<span class="sourceLineNo">128</span>   * Converts the given ThreadPoolExecutor into an ExecutorService that exits<a name="line.128"></a>
<span class="sourceLineNo">129</span>   * when the application is complete.  It does so by using daemon threads and<a name="line.129"></a>
<span class="sourceLineNo">130</span>   * adding a shutdown hook to wait for their completion.<a name="line.130"></a>
<span class="sourceLineNo">131</span>   *<a name="line.131"></a>
<span class="sourceLineNo">132</span>   * &lt;p&gt;This method waits 120 seconds before continuing with JVM termination,<a name="line.132"></a>
<span class="sourceLineNo">133</span>   * even if the executor has not finished its work.<a name="line.133"></a>
<span class="sourceLineNo">134</span>   *<a name="line.134"></a>
<span class="sourceLineNo">135</span>   * &lt;p&gt;This is mainly for fixed thread pools.<a name="line.135"></a>
<span class="sourceLineNo">136</span>   * See {@link Executors#newFixedThreadPool(int)}.<a name="line.136"></a>
<span class="sourceLineNo">137</span>   *<a name="line.137"></a>
<span class="sourceLineNo">138</span>   * @param executor the executor to modify to make sure it exits when the<a name="line.138"></a>
<span class="sourceLineNo">139</span>   *        application is finished<a name="line.139"></a>
<span class="sourceLineNo">140</span>   * @return an unmodifiable version of the input which will not hang the JVM<a name="line.140"></a>
<span class="sourceLineNo">141</span>   */<a name="line.141"></a>
<span class="sourceLineNo">142</span>  @Beta<a name="line.142"></a>
<span class="sourceLineNo">143</span>  public static ExecutorService getExitingExecutorService(ThreadPoolExecutor executor) {<a name="line.143"></a>
<span class="sourceLineNo">144</span>    return new Application().getExitingExecutorService(executor);<a name="line.144"></a>
<span class="sourceLineNo">145</span>  }<a name="line.145"></a>
<span class="sourceLineNo">146</span><a name="line.146"></a>
<span class="sourceLineNo">147</span>  /**<a name="line.147"></a>
<span class="sourceLineNo">148</span>   * Converts the given ThreadPoolExecutor into a ScheduledExecutorService that<a name="line.148"></a>
<span class="sourceLineNo">149</span>   * exits when the application is complete.  It does so by using daemon threads<a name="line.149"></a>
<span class="sourceLineNo">150</span>   * and adding a shutdown hook to wait for their completion.<a name="line.150"></a>
<span class="sourceLineNo">151</span>   *<a name="line.151"></a>
<span class="sourceLineNo">152</span>   * &lt;p&gt;This method waits 120 seconds before continuing with JVM termination,<a name="line.152"></a>
<span class="sourceLineNo">153</span>   * even if the executor has not finished its work.<a name="line.153"></a>
<span class="sourceLineNo">154</span>   *<a name="line.154"></a>
<span class="sourceLineNo">155</span>   * &lt;p&gt;This is mainly for fixed thread pools.<a name="line.155"></a>
<span class="sourceLineNo">156</span>   * See {@link Executors#newScheduledThreadPool(int)}.<a name="line.156"></a>
<span class="sourceLineNo">157</span>   *<a name="line.157"></a>
<span class="sourceLineNo">158</span>   * @param executor the executor to modify to make sure it exits when the<a name="line.158"></a>
<span class="sourceLineNo">159</span>   *        application is finished<a name="line.159"></a>
<span class="sourceLineNo">160</span>   * @return an unmodifiable version of the input which will not hang the JVM<a name="line.160"></a>
<span class="sourceLineNo">161</span>   */<a name="line.161"></a>
<span class="sourceLineNo">162</span>  @Beta<a name="line.162"></a>
<span class="sourceLineNo">163</span>  public static ScheduledExecutorService getExitingScheduledExecutorService(<a name="line.163"></a>
<span class="sourceLineNo">164</span>      ScheduledThreadPoolExecutor executor) {<a name="line.164"></a>
<span class="sourceLineNo">165</span>    return new Application().getExitingScheduledExecutorService(executor);<a name="line.165"></a>
<span class="sourceLineNo">166</span>  }<a name="line.166"></a>
<span class="sourceLineNo">167</span><a name="line.167"></a>
<span class="sourceLineNo">168</span>  /** Represents the current application to register shutdown hooks. */<a name="line.168"></a>
<span class="sourceLineNo">169</span>  @VisibleForTesting static class Application {<a name="line.169"></a>
<span class="sourceLineNo">170</span><a name="line.170"></a>
<span class="sourceLineNo">171</span>    final ExecutorService getExitingExecutorService(<a name="line.171"></a>
<span class="sourceLineNo">172</span>        ThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {<a name="line.172"></a>
<span class="sourceLineNo">173</span>      useDaemonThreadFactory(executor);<a name="line.173"></a>
<span class="sourceLineNo">174</span>      ExecutorService service = Executors.unconfigurableExecutorService(executor);<a name="line.174"></a>
<span class="sourceLineNo">175</span>      addDelayedShutdownHook(service, terminationTimeout, timeUnit);<a name="line.175"></a>
<span class="sourceLineNo">176</span>      return service;<a name="line.176"></a>
<span class="sourceLineNo">177</span>    }<a name="line.177"></a>
<span class="sourceLineNo">178</span><a name="line.178"></a>
<span class="sourceLineNo">179</span>    final ScheduledExecutorService getExitingScheduledExecutorService(<a name="line.179"></a>
<span class="sourceLineNo">180</span>        ScheduledThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit) {<a name="line.180"></a>
<span class="sourceLineNo">181</span>      useDaemonThreadFactory(executor);<a name="line.181"></a>
<span class="sourceLineNo">182</span>      ScheduledExecutorService service = Executors.unconfigurableScheduledExecutorService(executor);<a name="line.182"></a>
<span class="sourceLineNo">183</span>      addDelayedShutdownHook(service, terminationTimeout, timeUnit);<a name="line.183"></a>
<span class="sourceLineNo">184</span>      return service;<a name="line.184"></a>
<span class="sourceLineNo">185</span>    }<a name="line.185"></a>
<span class="sourceLineNo">186</span><a name="line.186"></a>
<span class="sourceLineNo">187</span>    final void addDelayedShutdownHook(<a name="line.187"></a>
<span class="sourceLineNo">188</span>        final ExecutorService service, final long terminationTimeout, final TimeUnit timeUnit) {<a name="line.188"></a>
<span class="sourceLineNo">189</span>      checkNotNull(service);<a name="line.189"></a>
<span class="sourceLineNo">190</span>      checkNotNull(timeUnit);<a name="line.190"></a>
<span class="sourceLineNo">191</span>      addShutdownHook(MoreExecutors.newThread("DelayedShutdownHook-for-" + service, new Runnable() {<a name="line.191"></a>
<span class="sourceLineNo">192</span>        @Override<a name="line.192"></a>
<span class="sourceLineNo">193</span>        public void run() {<a name="line.193"></a>
<span class="sourceLineNo">194</span>          try {<a name="line.194"></a>
<span class="sourceLineNo">195</span>            // We'd like to log progress and failures that may arise in the<a name="line.195"></a>
<span class="sourceLineNo">196</span>            // following code, but unfortunately the behavior of logging<a name="line.196"></a>
<span class="sourceLineNo">197</span>            // is undefined in shutdown hooks.<a name="line.197"></a>
<span class="sourceLineNo">198</span>            // This is because the logging code installs a shutdown hook of its<a name="line.198"></a>
<span class="sourceLineNo">199</span>            // own. See Cleaner class inside {@link LogManager}.<a name="line.199"></a>
<span class="sourceLineNo">200</span>            service.shutdown();<a name="line.200"></a>
<span class="sourceLineNo">201</span>            service.awaitTermination(terminationTimeout, timeUnit);<a name="line.201"></a>
<span class="sourceLineNo">202</span>          } catch (InterruptedException ignored) {<a name="line.202"></a>
<span class="sourceLineNo">203</span>            // We're shutting down anyway, so just ignore.<a name="line.203"></a>
<span class="sourceLineNo">204</span>          }<a name="line.204"></a>
<span class="sourceLineNo">205</span>        }<a name="line.205"></a>
<span class="sourceLineNo">206</span>      }));<a name="line.206"></a>
<span class="sourceLineNo">207</span>    }<a name="line.207"></a>
<span class="sourceLineNo">208</span><a name="line.208"></a>
<span class="sourceLineNo">209</span>    final ExecutorService getExitingExecutorService(ThreadPoolExecutor executor) {<a name="line.209"></a>
<span class="sourceLineNo">210</span>      return getExitingExecutorService(executor, 120, TimeUnit.SECONDS);<a name="line.210"></a>
<span class="sourceLineNo">211</span>    }<a name="line.211"></a>
<span class="sourceLineNo">212</span><a name="line.212"></a>
<span class="sourceLineNo">213</span>    final ScheduledExecutorService getExitingScheduledExecutorService(<a name="line.213"></a>
<span class="sourceLineNo">214</span>        ScheduledThreadPoolExecutor executor) {<a name="line.214"></a>
<span class="sourceLineNo">215</span>      return getExitingScheduledExecutorService(executor, 120, TimeUnit.SECONDS);<a name="line.215"></a>
<span class="sourceLineNo">216</span>    }<a name="line.216"></a>
<span class="sourceLineNo">217</span><a name="line.217"></a>
<span class="sourceLineNo">218</span>    @VisibleForTesting void addShutdownHook(Thread hook) {<a name="line.218"></a>
<span class="sourceLineNo">219</span>      Runtime.getRuntime().addShutdownHook(hook);<a name="line.219"></a>
<span class="sourceLineNo">220</span>    }<a name="line.220"></a>
<span class="sourceLineNo">221</span>  }<a name="line.221"></a>
<span class="sourceLineNo">222</span><a name="line.222"></a>
<span class="sourceLineNo">223</span>  private static void useDaemonThreadFactory(ThreadPoolExecutor executor) {<a name="line.223"></a>
<span class="sourceLineNo">224</span>    executor.setThreadFactory(new ThreadFactoryBuilder()<a name="line.224"></a>
<span class="sourceLineNo">225</span>        .setDaemon(true)<a name="line.225"></a>
<span class="sourceLineNo">226</span>        .setThreadFactory(executor.getThreadFactory())<a name="line.226"></a>
<span class="sourceLineNo">227</span>        .build());<a name="line.227"></a>
<span class="sourceLineNo">228</span>  }<a name="line.228"></a>
<span class="sourceLineNo">229</span><a name="line.229"></a>
<span class="sourceLineNo">230</span>  /**<a name="line.230"></a>
<span class="sourceLineNo">231</span>   * Creates an executor service that runs each task in the thread<a name="line.231"></a>
<span class="sourceLineNo">232</span>   * that invokes {@code execute/submit}, as in {@link CallerRunsPolicy}  This<a name="line.232"></a>
<span class="sourceLineNo">233</span>   * applies both to individually submitted tasks and to collections of tasks<a name="line.233"></a>
<span class="sourceLineNo">234</span>   * submitted via {@code invokeAll} or {@code invokeAny}.  In the latter case,<a name="line.234"></a>
<span class="sourceLineNo">235</span>   * tasks will run serially on the calling thread.  Tasks are run to<a name="line.235"></a>
<span class="sourceLineNo">236</span>   * completion before a {@code Future} is returned to the caller (unless the<a name="line.236"></a>
<span class="sourceLineNo">237</span>   * executor has been shutdown).<a name="line.237"></a>
<span class="sourceLineNo">238</span>   *<a name="line.238"></a>
<span class="sourceLineNo">239</span>   * &lt;p&gt;Although all tasks are immediately executed in the thread that<a name="line.239"></a>
<span class="sourceLineNo">240</span>   * submitted the task, this {@code ExecutorService} imposes a small<a name="line.240"></a>
<span class="sourceLineNo">241</span>   * locking overhead on each task submission in order to implement shutdown<a name="line.241"></a>
<span class="sourceLineNo">242</span>   * and termination behavior.<a name="line.242"></a>
<span class="sourceLineNo">243</span>   *<a name="line.243"></a>
<span class="sourceLineNo">244</span>   * &lt;p&gt;The implementation deviates from the {@code ExecutorService}<a name="line.244"></a>
<span class="sourceLineNo">245</span>   * specification with regards to the {@code shutdownNow} method.  First,<a name="line.245"></a>
<span class="sourceLineNo">246</span>   * "best-effort" with regards to canceling running tasks is implemented<a name="line.246"></a>
<span class="sourceLineNo">247</span>   * as "no-effort".  No interrupts or other attempts are made to stop<a name="line.247"></a>
<span class="sourceLineNo">248</span>   * threads executing tasks.  Second, the returned list will always be empty,<a name="line.248"></a>
<span class="sourceLineNo">249</span>   * as any submitted task is considered to have started execution.<a name="line.249"></a>
<span class="sourceLineNo">250</span>   * This applies also to tasks given to {@code invokeAll} or {@code invokeAny}<a name="line.250"></a>
<span class="sourceLineNo">251</span>   * which are pending serial execution, even the subset of the tasks that<a name="line.251"></a>
<span class="sourceLineNo">252</span>   * have not yet started execution.  It is unclear from the<a name="line.252"></a>
<span class="sourceLineNo">253</span>   * {@code ExecutorService} specification if these should be included, and<a name="line.253"></a>
<span class="sourceLineNo">254</span>   * it's much easier to implement the interpretation that they not be.<a name="line.254"></a>
<span class="sourceLineNo">255</span>   * Finally, a call to {@code shutdown} or {@code shutdownNow} may result<a name="line.255"></a>
<span class="sourceLineNo">256</span>   * in concurrent calls to {@code invokeAll/invokeAny} throwing<a name="line.256"></a>
<span class="sourceLineNo">257</span>   * RejectedExecutionException, although a subset of the tasks may already<a name="line.257"></a>
<span class="sourceLineNo">258</span>   * have been executed.<a name="line.258"></a>
<span class="sourceLineNo">259</span>   *<a name="line.259"></a>
<span class="sourceLineNo">260</span>   * @since 10.0 (&lt;a href="http://code.google.com/p/guava-libraries/wiki/Compatibility"<a name="line.260"></a>
<span class="sourceLineNo">261</span>   *        &gt;mostly source-compatible&lt;/a&gt; since 3.0)<a name="line.261"></a>
<span class="sourceLineNo">262</span>   */<a name="line.262"></a>
<span class="sourceLineNo">263</span>  public static ListeningExecutorService sameThreadExecutor() {<a name="line.263"></a>
<span class="sourceLineNo">264</span>    return new SameThreadExecutorService();<a name="line.264"></a>
<span class="sourceLineNo">265</span>  }<a name="line.265"></a>
<span class="sourceLineNo">266</span><a name="line.266"></a>
<span class="sourceLineNo">267</span>  // See sameThreadExecutor javadoc for behavioral notes.<a name="line.267"></a>
<span class="sourceLineNo">268</span>  private static class SameThreadExecutorService<a name="line.268"></a>
<span class="sourceLineNo">269</span>      extends AbstractListeningExecutorService {<a name="line.269"></a>
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<span class="sourceLineNo">271</span>     * Lock used whenever accessing the state variables<a name="line.271"></a>
<span class="sourceLineNo">272</span>     * (runningTasks, shutdown, terminationCondition) of the executor<a name="line.272"></a>
<span class="sourceLineNo">273</span>     */<a name="line.273"></a>
<span class="sourceLineNo">274</span>    private final Lock lock = new ReentrantLock();<a name="line.274"></a>
<span class="sourceLineNo">275</span><a name="line.275"></a>
<span class="sourceLineNo">276</span>    /** Signaled after the executor is shutdown and running tasks are done */<a name="line.276"></a>
<span class="sourceLineNo">277</span>    private final Condition termination = lock.newCondition();<a name="line.277"></a>
<span class="sourceLineNo">278</span><a name="line.278"></a>
<span class="sourceLineNo">279</span>    /*<a name="line.279"></a>
<span class="sourceLineNo">280</span>     * Conceptually, these two variables describe the executor being in<a name="line.280"></a>
<span class="sourceLineNo">281</span>     * one of three states:<a name="line.281"></a>
<span class="sourceLineNo">282</span>     *   - Active: shutdown == false<a name="line.282"></a>
<span class="sourceLineNo">283</span>     *   - Shutdown: runningTasks &gt; 0 and shutdown == true<a name="line.283"></a>
<span class="sourceLineNo">284</span>     *   - Terminated: runningTasks == 0 and shutdown == true<a name="line.284"></a>
<span class="sourceLineNo">285</span>     */<a name="line.285"></a>
<span class="sourceLineNo">286</span>    private int runningTasks = 0;<a name="line.286"></a>
<span class="sourceLineNo">287</span>    private boolean shutdown = false;<a name="line.287"></a>
<span class="sourceLineNo">288</span><a name="line.288"></a>
<span class="sourceLineNo">289</span>    @Override<a name="line.289"></a>
<span class="sourceLineNo">290</span>    public void execute(Runnable command) {<a name="line.290"></a>
<span class="sourceLineNo">291</span>      startTask();<a name="line.291"></a>
<span class="sourceLineNo">292</span>      try {<a name="line.292"></a>
<span class="sourceLineNo">293</span>        command.run();<a name="line.293"></a>
<span class="sourceLineNo">294</span>      } finally {<a name="line.294"></a>
<span class="sourceLineNo">295</span>        endTask();<a name="line.295"></a>
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<span class="sourceLineNo">297</span>    }<a name="line.297"></a>
<span class="sourceLineNo">298</span><a name="line.298"></a>
<span class="sourceLineNo">299</span>    @Override<a name="line.299"></a>
<span class="sourceLineNo">300</span>    public boolean isShutdown() {<a name="line.300"></a>
<span class="sourceLineNo">301</span>      lock.lock();<a name="line.301"></a>
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<span class="sourceLineNo">303</span>        return shutdown;<a name="line.303"></a>
<span class="sourceLineNo">304</span>      } finally {<a name="line.304"></a>
<span class="sourceLineNo">305</span>        lock.unlock();<a name="line.305"></a>
<span class="sourceLineNo">306</span>      }<a name="line.306"></a>
<span class="sourceLineNo">307</span>    }<a name="line.307"></a>
<span class="sourceLineNo">308</span><a name="line.308"></a>
<span class="sourceLineNo">309</span>    @Override<a name="line.309"></a>
<span class="sourceLineNo">310</span>    public void shutdown() {<a name="line.310"></a>
<span class="sourceLineNo">311</span>      lock.lock();<a name="line.311"></a>
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<span class="sourceLineNo">313</span>        shutdown = true;<a name="line.313"></a>
<span class="sourceLineNo">314</span>      } finally {<a name="line.314"></a>
<span class="sourceLineNo">315</span>        lock.unlock();<a name="line.315"></a>
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<span class="sourceLineNo">318</span><a name="line.318"></a>
<span class="sourceLineNo">319</span>    // See sameThreadExecutor javadoc for unusual behavior of this method.<a name="line.319"></a>
<span class="sourceLineNo">320</span>    @Override<a name="line.320"></a>
<span class="sourceLineNo">321</span>    public List&lt;Runnable&gt; shutdownNow() {<a name="line.321"></a>
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<span class="sourceLineNo">323</span>      return Collections.emptyList();<a name="line.323"></a>
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<span class="sourceLineNo">326</span>    @Override<a name="line.326"></a>
<span class="sourceLineNo">327</span>    public boolean isTerminated() {<a name="line.327"></a>
<span class="sourceLineNo">328</span>      lock.lock();<a name="line.328"></a>
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<span class="sourceLineNo">330</span>        return shutdown &amp;&amp; runningTasks == 0;<a name="line.330"></a>
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<span class="sourceLineNo">332</span>        lock.unlock();<a name="line.332"></a>
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<span class="sourceLineNo">335</span><a name="line.335"></a>
<span class="sourceLineNo">336</span>    @Override<a name="line.336"></a>
<span class="sourceLineNo">337</span>    public boolean awaitTermination(long timeout, TimeUnit unit)<a name="line.337"></a>
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<span class="sourceLineNo">340</span>      lock.lock();<a name="line.340"></a>
<span class="sourceLineNo">341</span>      try {<a name="line.341"></a>
<span class="sourceLineNo">342</span>        for (;;) {<a name="line.342"></a>
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<span class="sourceLineNo">345</span>          } else if (nanos &lt;= 0) {<a name="line.345"></a>
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<span class="sourceLineNo">356</span>    /**<a name="line.356"></a>
<span class="sourceLineNo">357</span>     * Checks if the executor has been shut down and increments the running<a name="line.357"></a>
<span class="sourceLineNo">358</span>     * task count.<a name="line.358"></a>
<span class="sourceLineNo">359</span>     *<a name="line.359"></a>
<span class="sourceLineNo">360</span>     * @throws RejectedExecutionException if the executor has been previously<a name="line.360"></a>
<span class="sourceLineNo">361</span>     *         shutdown<a name="line.361"></a>
<span class="sourceLineNo">362</span>     */<a name="line.362"></a>
<span class="sourceLineNo">363</span>    private void startTask() {<a name="line.363"></a>
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<span class="sourceLineNo">365</span>      try {<a name="line.365"></a>
<span class="sourceLineNo">366</span>        if (isShutdown()) {<a name="line.366"></a>
<span class="sourceLineNo">367</span>          throw new RejectedExecutionException("Executor already shutdown");<a name="line.367"></a>
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<span class="sourceLineNo">371</span>        lock.unlock();<a name="line.371"></a>
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<span class="sourceLineNo">374</span><a name="line.374"></a>
<span class="sourceLineNo">375</span>    /**<a name="line.375"></a>
<span class="sourceLineNo">376</span>     * Decrements the running task count.<a name="line.376"></a>
<span class="sourceLineNo">377</span>     */<a name="line.377"></a>
<span class="sourceLineNo">378</span>    private void endTask() {<a name="line.378"></a>
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<span class="sourceLineNo">380</span>      try {<a name="line.380"></a>
<span class="sourceLineNo">381</span>        runningTasks--;<a name="line.381"></a>
<span class="sourceLineNo">382</span>        if (isTerminated()) {<a name="line.382"></a>
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<span class="sourceLineNo">386</span>        lock.unlock();<a name="line.386"></a>
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<span class="sourceLineNo">391</span>  /**<a name="line.391"></a>
<span class="sourceLineNo">392</span>   * Creates an {@link ExecutorService} whose {@code submit} and {@code<a name="line.392"></a>
<span class="sourceLineNo">393</span>   * invokeAll} methods submit {@link ListenableFutureTask} instances to the<a name="line.393"></a>
<span class="sourceLineNo">394</span>   * given delegate executor. Those methods, as well as {@code execute} and<a name="line.394"></a>
<span class="sourceLineNo">395</span>   * {@code invokeAny}, are implemented in terms of calls to {@code<a name="line.395"></a>
<span class="sourceLineNo">396</span>   * delegate.execute}. All other methods are forwarded unchanged to the<a name="line.396"></a>
<span class="sourceLineNo">397</span>   * delegate. This implies that the returned {@code ListeningExecutorService}<a name="line.397"></a>
<span class="sourceLineNo">398</span>   * never calls the delegate's {@code submit}, {@code invokeAll}, and {@code<a name="line.398"></a>
<span class="sourceLineNo">399</span>   * invokeAny} methods, so any special handling of tasks must be implemented in<a name="line.399"></a>
<span class="sourceLineNo">400</span>   * the delegate's {@code execute} method or by wrapping the returned {@code<a name="line.400"></a>
<span class="sourceLineNo">401</span>   * ListeningExecutorService}.<a name="line.401"></a>
<span class="sourceLineNo">402</span>   *<a name="line.402"></a>
<span class="sourceLineNo">403</span>   * &lt;p&gt;If the delegate executor was already an instance of {@code<a name="line.403"></a>
<span class="sourceLineNo">404</span>   * ListeningExecutorService}, it is returned untouched, and the rest of this<a name="line.404"></a>
<span class="sourceLineNo">405</span>   * documentation does not apply.<a name="line.405"></a>
<span class="sourceLineNo">406</span>   *<a name="line.406"></a>
<span class="sourceLineNo">407</span>   * @since 10.0<a name="line.407"></a>
<span class="sourceLineNo">408</span>   */<a name="line.408"></a>
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<span class="sourceLineNo">412</span>        ? (ListeningExecutorService) delegate<a name="line.412"></a>
<span class="sourceLineNo">413</span>        : (delegate instanceof ScheduledExecutorService)<a name="line.413"></a>
<span class="sourceLineNo">414</span>        ? new ScheduledListeningDecorator((ScheduledExecutorService) delegate)<a name="line.414"></a>
<span class="sourceLineNo">415</span>        : new ListeningDecorator(delegate);<a name="line.415"></a>
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<span class="sourceLineNo">418</span>  /**<a name="line.418"></a>
<span class="sourceLineNo">419</span>   * Creates a {@link ScheduledExecutorService} whose {@code submit} and {@code<a name="line.419"></a>
<span class="sourceLineNo">420</span>   * invokeAll} methods submit {@link ListenableFutureTask} instances to the<a name="line.420"></a>
<span class="sourceLineNo">421</span>   * given delegate executor. Those methods, as well as {@code execute} and<a name="line.421"></a>
<span class="sourceLineNo">422</span>   * {@code invokeAny}, are implemented in terms of calls to {@code<a name="line.422"></a>
<span class="sourceLineNo">423</span>   * delegate.execute}. All other methods are forwarded unchanged to the<a name="line.423"></a>
<span class="sourceLineNo">424</span>   * delegate. This implies that the returned {@code<a name="line.424"></a>
<span class="sourceLineNo">425</span>   * SchedulingListeningExecutorService} never calls the delegate's {@code<a name="line.425"></a>
<span class="sourceLineNo">426</span>   * submit}, {@code invokeAll}, and {@code invokeAny} methods, so any special<a name="line.426"></a>
<span class="sourceLineNo">427</span>   * handling of tasks must be implemented in the delegate's {@code execute}<a name="line.427"></a>
<span class="sourceLineNo">428</span>   * method or by wrapping the returned {@code<a name="line.428"></a>
<span class="sourceLineNo">429</span>   * SchedulingListeningExecutorService}.<a name="line.429"></a>
<span class="sourceLineNo">430</span>   *<a name="line.430"></a>
<span class="sourceLineNo">431</span>   * &lt;p&gt;If the delegate executor was already an instance of {@code<a name="line.431"></a>
<span class="sourceLineNo">432</span>   * ListeningScheduledExecutorService}, it is returned untouched, and the rest<a name="line.432"></a>
<span class="sourceLineNo">433</span>   * of this documentation does not apply.<a name="line.433"></a>
<span class="sourceLineNo">434</span>   *<a name="line.434"></a>
<span class="sourceLineNo">435</span>   * @since 10.0<a name="line.435"></a>
<span class="sourceLineNo">436</span>   */<a name="line.436"></a>
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<span class="sourceLineNo">439</span>    return (delegate instanceof ListeningScheduledExecutorService)<a name="line.439"></a>
<span class="sourceLineNo">440</span>        ? (ListeningScheduledExecutorService) delegate<a name="line.440"></a>
<span class="sourceLineNo">441</span>        : new ScheduledListeningDecorator(delegate);<a name="line.441"></a>
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<span class="sourceLineNo">445</span>      extends AbstractListeningExecutorService {<a name="line.445"></a>
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<span class="sourceLineNo">447</span><a name="line.447"></a>
<span class="sourceLineNo">448</span>    ListeningDecorator(ExecutorService delegate) {<a name="line.448"></a>
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<span class="sourceLineNo">452</span>    @Override<a name="line.452"></a>
<span class="sourceLineNo">453</span>    public boolean awaitTermination(long timeout, TimeUnit unit)<a name="line.453"></a>
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<span class="sourceLineNo">459</span>    public boolean isShutdown() {<a name="line.459"></a>
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<span class="sourceLineNo">463</span>    @Override<a name="line.463"></a>
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<span class="sourceLineNo">468</span>    @Override<a name="line.468"></a>
<span class="sourceLineNo">469</span>    public void shutdown() {<a name="line.469"></a>
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<span class="sourceLineNo">486</span>    @SuppressWarnings("hiding")<a name="line.486"></a>
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<span class="sourceLineNo">488</span><a name="line.488"></a>
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<span class="sourceLineNo">493</span><a name="line.493"></a>
<span class="sourceLineNo">494</span>    @Override<a name="line.494"></a>
<span class="sourceLineNo">495</span>    public ScheduledFuture&lt;?&gt; schedule(<a name="line.495"></a>
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